This invention relates to shaft couplings, and more particularly, to disc pack couplings for transmitting torque between two shafts approximately aligned on a shaft axis.
Flexible disc pack couplings, such as Thomas Flexible Disc Couplings sold by Rexnord Industries, Inc., Milwaukee, Wis., are known in the art for transmitting torque between adjacent generally axially aligned first and second shafts. These couplings typically include a plurality of stacked coaxial discs interposed between a pair of hubs. A first hub is fixed to one end of the first shaft, and a second hub facing the first hub is fixed to the adjacent end of the second shaft. A plurality of first bolts extending through holes formed through the first hub extends through holes formed in the disc pack and oversized holes formed through the second hub to fix the disc pack to the first hub. A plurality of second bolts extending through holes formed through the second hub extends through holes formed in the disc pack and oversized holes formed through the first hub to fix the disc pack to the second hub.
The stacked discs include a plurality of inner discs sandwiched between a pair of outermost discs to form a disc pack. The pack can be formed at the time of installation by gathering and aligning a desired number of individual discs. Alternatively, the discs can be provided as a unitized pack of discs joined together. In one embodiment, a unitized pack is formed by pressing bushings in the holes formed through the discs. The bushings are fixed in the holes by an interference fit, and the discs are held together by the frictional engagement with the bushings. The bushings are installed from both sides of the disc pack in an alternating sequence to prevent an undesirable situation that can occur if the bushings are installed from the same side, wherein the outermost discs in the pack could slip off the end of the bushings, complicating the installation of the disc pack between the hubs.
Installation of the discs between the hubs includes inserting a washer aligned with each hole in the disc pack between the disc pack and a nut tightened on the bolt while holding the disc pack holes aligned with holes formed in the hubs and inserting a bolt through the aligned disc pack holes, hub holes, and washers. This is very difficult to do, especially when one or more of the outermost discs slips off the end of a bushing when attempting to maintain all of the components in alignment in order to insert a bolt through the holes formed in the components. Accordingly, a need exists for an improved unitized disc pack that simplifies the installation procedure.